1.Make tomato onion raita. Cook mustard seeds in heated small frying pan until seeds begin to pop. Combine seeds in medium bowl with remaining ingredients.
2.Place tapioca in large heatproof bowl, cover with boiling water. Stand 10 minutes, drain.
3.Meanwhile, heat oil in small frying pan, cook cumin and turmeric, stirring, until fragrant.
4.Boil, steam or microwave potato until tender, drain. Mash potato in large bowl then stir in tapioca, cumin, turmeric, nuts, coriander, chilli and ginger. Shape heaped tablespoons of potato mixture into patty-size cakes. Heat extra oil in large frying pan, shallow-fry potato cakes, in batches, until browned. Drain on absorbent paper, serve with raita.
A grain often used for puddings and desserts, and as a thickening agent in cooking, tapioca is sourced from the root of the cassava plant (unlike sago, with which it is often confused, which comes from a variety of palm).Note